We previously found transcriptional inhibition of the proliferating cell nuclear antigen (PCNA) and D-raf (Drosophila homolog of the human c-raf-1 gene) genes by ursolic acid in Drosophila Kc cells. In this study, we also confirmed the fact in vivo by using transgenic flies. To know the mechanism of repression of PCNA and D-raf promoter activities by ursolic acid, we examined the effect of 20-OH ecdysone similar to the structure of ursolic acid on expression of these genes. 20-OH ecdysone also inhibit expression of the PCNA and D-raf genes. The inhibition effect of 20-OH ecdysone on expression of these genes was not shown at the tested concentration higher than 1 μM in both Drosopihila Kc cells and transgenic flies, while ursolic acid showed the dose dependent inhibition effect.